There certainly are illustrated editions of The Silmarillion. Most of them are foreign editions of the Ted Nasmith-illustrated Silmarillions. By example, I have the 1998 Nasmith-illustrated one in English, French, Korean, Danish, Hungarian and Spanish.

As for the moment, I am working on my website which will show my collection of foreign Silmarillions. I can say that building a website is more difficult than I thought! Just keep an eye on http://www.silmarillion-project.org the following months, I shall do my best to make it something useful and beautiful.